ATC70 Air Filter Question

[sojukrum]

Fellas,

I've got an ATC 70 I'm restoring, and wanted to run the open airfilter. I took the stock cannister off. I just got it all back together, but can't seem to get it dialed in. When I asked the Honda service dept about it, they of course told me I needed to put the cannister back on. They said the bike is running too lean with the open air filter?? Well, I don't about that as I've seen many guys running the open airfilter. Do you all have any advice as to running this type of air filter on the 70? Different jets, etc.? The rest of the engine is all stock. Any info would be much appreciated!

[RedRider_AK]

Yep, you need to rejet it. A few sizes more than stock, to compensate for better airflow.

[SYKO]

I put a bigger carb on my daughters trx 70 (same thing) and it ran like crap just testing without a filter, I put a clamp on filter from JL and this little beast rips! she loves it! didnt even mess with the carb!

[sojukrum]

Thanks guys, appreciate the input. Any suggestions for the new jets? Where to get them? I usually buy all my parts at Beatrice Cycle, but I didn't notice jets for the open airfilter. You all have any suggestions?

[blue27]

Beatrice has them 3.50 each look under ATC 70 Carb section. Find out what you have now and get the next two sizes bigger. Try the first one and do a plug check, if its still lean then jump to the next one bigger. You should only need to go to the next size up but... I like to keep some around. Depending on the year (if it is a 78-85) it should be a #58 size jet know.